Not to be taken by pregnant or lactating women. Rare side
effects include occasional gastrointestinal distress, nausea, itching,
and headache. Milk thistle should be avoided by individuals with
allergies to members of the aster (Compositea/Asteraceae) family,
daisies, artichoke, kiwi or thistle.

Some studies have reported that milk thistle can affect the
way that the liver breaks down medications metabolized by the
cytochrome P450 system, altering the effects of these medications and
possibly the dose needed for treatment. Certain ingredients may
interfere with certain heart, blood thinning, antidiarrheal, and cold or
hay fever medications. Consult your physician for more information.